Field of the Invention
The present invention relates to an aqueous ink, an ink cartridge, and an ink jet recording method.
Description of the Related Art
In recent years, inks containing pigments (pigment inks) as coloring materials have been widely used as the inks used for the ink jet recording method. In order to give glossy images such as photographs, an ink containing a resin-dispersed pigment in which a pigment is dispersed by a resin (resin dispersant) is typically used. If the ink containing the resin-dispersed pigment is used, highly tough images can be recorded because the pigment is present in the form of particles in the ink. However, the images recorded with the pigment inks unfortunately have lower gloss clarity than those of images recorded with dye inks in which dyes are dissolved in an aqueous medium. The “gloss clarity” is an indicator of the image characteristics commonly used for evaluating glossy images and an indicator of clearness and distinctness of an image recorded on the surface of a recording medium.
To solve that problem, various techniques have been disclosed. In one of the techniques, a silicone-containing surfactant or a fluorinated surfactant is added to lower the surface tension of an ink, and thus the wettability and permeability of the ink to a recording medium is improved. For example, an ink containing a silicone-containing surfactant or a fluorinated surfactant has been disclosed. The ink enables recording of images having excellent uniformity, void resistance, glossiness, and scratch resistance (Japanese Patent Application Laid-Open No. 2012-184376).
Moreover, by combining the three primary color inks with other inks than the three primary color inks (particular color inks), such as a red ink, a green ink, a blue ink, an orange ink, and a violet ink, the expansion of the color reproduction region of images have been studied. For example, an ink set including a red ink containing C.I. Pigment Red 254 (Japanese Patent Application Laid-Open No. 2004-155830) and a blue ink containing C.I. Pigment Violet (Japanese Patent Application Laid-Open No. 2005-112872) have been disclosed.
Meanwhile, aqueous inks may freeze depending on usage environments or transportation conditions of ink jet recording apparatuses, but the pigments are required to be stably dispersed even after melting. As an example of inks which can suppress freezing, an ink containing predetermined amounts of polyethylene glycol and diethylene glycol has been disclosed (Japanese Patent Application Laid-Open No. 2006-249203).